The Two-Tier Classification System
HDB divides renovation works into two broad categories. The first tier covers works that are generally acceptable without requiring the owner to file an application — these are typically cosmetic or maintenance-related changes that do not alter the flat's structural integrity, fire safety provisions, or shared building systems. The second tier covers works that must go through HDB's Renovation Permit system before any contractor is engaged.
The distinction is not always intuitive. For example, replacing floor tiles in a bedroom falls in the first tier if the existing screed is retained, but the moment the screed is hacked and re-laid, the project crosses into second-tier territory because it involves wet works and potential waterproofing obligations.
The full list of permitted and controlled renovation works is published on the HDB official website and updated periodically. Always verify the current version before submitting an application.
Works That Always Require a Permit
The following categories consistently require an approved application before work can begin. This list reflects HDB's published renovation guidelines as of early 2026, but individual circumstances may introduce additional requirements.
Structural and Wall Works
- Demolition or partial removal of any non-structural internal wall
- Creation of new doorway or window openings in an existing wall
- Installation of bay windows or sunken features that alter external façade lines
- Construction or removal of internal steps or raised flooring platforms
Wet Area and Waterproofing Works
- Full waterproofing membrane installation in bathrooms or kitchen
- Hacking and re-screed of bathroom or kitchen floors
- Relocation of floor trap positions
- Changes to the bathroom floor level relative to the corridor
Electrical and Mechanical Works
- Addition of new power points beyond minor modification
- Installation of additional circuit breakers or MCB additions
- Relocation of distribution boards
- Installation of exhaust fans penetrating external walls
Gas Works
- Any modification to existing gas piping
- Addition or relocation of gas points
- Conversion between gas cooking and electric cooking requiring new connections
How the Application Process Works
Renovation permit applications are submitted through HDB's e-Service portal by the appointed renovation contractor — not by the flat owner directly. This is an important distinction: the contractor must be a registered HDB renovation contractor, and the application must be submitted at least three working days before works commence. In practice, most applications take between one and three weeks to process.
Step-by-Step Application Flow
- Flat owner identifies the scope of works and engages a registered HDB renovation contractor
- Contractor prepares the renovation plan, including room dimensions and proposed changes
- Contractor submits the Renovation Permit application via HDB's e-Service portal
- HDB reviews the application and issues a Renovation Permit or requests clarification
- Upon permit issuance, the contractor displays the permit at the flat entrance throughout the renovation period
- Works commence within the approved timeframe
- Contractor carries out an end-of-renovation inspection if required
The issued Renovation Permit must be displayed at the flat's main entrance door throughout the renovation period. Failure to display the permit is itself a regulatory violation and can result in HDB stopping works on-site.
Typical Permit Processing Times
For standard residential renovations, HDB targets a processing time of approximately three to fifteen working days depending on the complexity of the works. Applications involving structural modifications, gas works, or alterations to fire safety components typically take longer and may require supplementary documentation such as an engineer's endorsement or contractor's professional indemnity declaration.
Owners should factor permit processing time into their renovation timeline before signing a contract with a contractor. Commencing works before a permit is issued — even if an application has been filed — is treated as a violation.
What Happens Without a Permit
HDB conducts periodic inspections and responds to neighbour complaints. When unauthorised renovation works are discovered, HDB may issue a Stop Work Order requiring all activity to cease immediately. The flat owner — not the contractor — bears primary responsibility for ensuring that all permit requirements are met.
Depending on the severity, HDB can require the owner to restore the flat to its original condition at the owner's cost. In cases where restoration is not feasible (for example, where a wall has been demolished and the flat's structural integrity is compromised), HDB may engage its own contractors and bill the owner for the rectification works.
Administrative financial penalties of up to $5,000 may also be imposed, and repeated violations can affect the owner's ability to carry out future renovations in the flat.
Exemptions and Special Cases
Flats that are more than 40 years old and classified as Design, Build and Sell Scheme (DBSS) units or older pre-1990s HDB blocks may have additional structural restrictions not applicable to newer flats. Owners of older flats should consult HDB's branch office directly before commissioning any works that involve walls or flooring, as the building's structural configuration may differ from standard block types.
Heritage flats in designated conservation areas — such as certain blocks in Queenstown and Toa Payoh — face additional constraints under Urban Redevelopment Authority (URA) guidelines on top of standard HDB renovation rules. In these cases, owners need to coordinate with both agencies before the renovation permit application can proceed.